This artificial riparian zone will be placed in the Colorado River near Diamond Creek, due to the best relative mixture of current, depth, and available sediment. We would ideally place this device on the bank of a linear section of river in order to maintain a large river flow through this zone while preventing collisions with river-goers (which curved sections may provoke).

In terms of larger debris, it is important to note that our device targets sediment suspended in water the most, which by its nature requires it to be small, usually less than 0.025mm. Larger sediment, which can extend up to 2mm and up, usually settles or lowers to the bottom in standard conditions due to their weight, and thus would not pose a problem for suffocating animals. Natural river currents tend to push out the smaller, suspended sediments out to the side of direct current, and from there, our system should be able to filter them out.

Testing exactly what ratio of sediment that can be filtered by each plant proved to be difficult due to lack of commercial tests in the current circumstance, however, we instead tested how the plants could filter out chemicals common to suspended sediment, such as ammonia. Ammonia particularly is common to sediment commonly due to loose fertilizer or bacterial breakdown in organic particulates. In our tests, we measured the rate at which ammonia can be filtered out of the water, and found that per hour, the plants could usually filter about 0.3 grams of ammonia. Extended to the entire system with 24 plants, our design would be able to filter out 7.2 grams of ammonia an hour, a great indicator that our plants could filter out sediment and its other contaminants at an appropriate rate.

The Colorado River at our chosen location, tends to demonstrate a large range of turbidity based on the current time and conditions, going as high as 2000 FNU and having an average at around 60 FNU. In order to calculate the amount of sediment per gallon, we used a reference from the Missouri River, and calculated the weight of sediment per gallon of water, as shown below. [1]
SSC = 1.8239(Turb)^0.984
At an average of 60FNU, we can expect a sediment density of 8.5536*10^-4 lb/gallon
At a maximum 2000FNU, sediment density can be expected to be 2.6596*10^-2 lb/gallon
One thing that is particular to note is that the Missouri River and the Colorado River do not share the same soil and type of sediment due to their different environments, so while we believe it is close, we do expect some error.

Maintenance is fortunately low for this design, ideally conducted by a certified diver or drone about monthly. Each month, the diver will spend roughly six hours evaluating the infrastructure of the design as well as the qualitative effectiveness. The limestone cartridges will be replaced based on the diver’s observations as well as plant trimmings or replacement. Overall cost of the labor amounts to zero as it is based on volunteer work. Each plant costs roughly fifteen dollars to replace and the limestone cartridges cost three dollars per replacement.

As mentioned earlier, sediment can often carry and coat itself with other impurities, whether it be chemicals from industrial or agricultural processes, heavy metals for mining, or, as you mentioned, oil. Fortunately, we curated our list of available plants so that they would not only be able to filter out sediment, but also other contaminants they may come with, usually uptaking them through their leaves in a process known as phytoremediation. Currently, the plants we would plan to use at the Colorado River are able to filter out general and heavy metals among more prominent chemicals such as lead, phosphorus, arsenic, and ammonia. In terms of oil, which proves to be a little more complex, we have found an available aquatic ferns that is able to readily absorb oil, but would require a lower current than available at our location.

We would ideally place the artificial riparian zone along the rank bank downstream of the confluence between the Colorado River and its branch of Diamond Creek, preferably along one of its’ straight edges. We found this spot to be effective because it maintained the levels of sediment pollution in the Colorado River while having an appropriate depth and current to build a proper structure. The flow of both branches past this system helps bring in the greatest volume of water to filter, and thus the most sediment to filter. Likewise, having it be straight helps guide the current through the design with the best flow of suspended sediment.
If extended to other rivers, the main conditions would be a relatively straight location that is deep and wide enough to build a system without obstructing the movement of fish and boats. While having it at a confluence could be strategic, it ultimately isn’t necessary.

In order to prevent our system from malfunctioning due to increased water flow, each section has validated it’s structural strength. The limestone cartridges, infrastructure, nursery, and growth tray sections of the system are all fastened securely, such that a flash flood or similar event will likely not affect them. To secure our plants such that they wouldn’t be swept away in this event, they will be grown and rooted into the growth tray with rock wool before being lowered into the river and installed. The ability of rockwool to maintain a hold on rooted plants has been verified by a scholarly article within the gardening community [1], and as such should be able to avoid being uprooted even during high current periods of time.

In terms of design pivots (I really like this question), our design didn’t change much, but it did feature an important shift in the very beginning. At this point, we were still looking at how we could restore or protect riparian zones as natural filters, and we were specifically combining remediational habitats and floating river farms. Remidiational habitats offered great surface area as they were often built by digging out a parallel branch to the river, they proved overly costly and only received part of the water flow, while floating river farms could filter out sediment directly, but were often too small and obstructive to anything else. Initially, this led our designs to be too horizontally large, taking up much of the surface of the river, which could obstruct the movement of wildlife and boats. In order to offset the requirements of space, an idea was formed to add surface area by creating additional layers vertically, underwater.
Thus, we created a layered riparian zone, and in order to ensure that it could stand and function underwater, we consulted with many experts in dock-making, as well as hydroponics. Once we were satisfied that it could be done, we created a new list of plants that could survive underwater while filtering out pollutants, grouping them on their most effective elevations. Once we were at this momentum, our design grew to accompany a nursery and filters with the available new space.

Thank you Alina!
Because the design takes a more natural approach to filtering the rivers with plants, we do not expect much maintenance or upkeep along its lifespan. The most money and time would be spent toward the system’s construction.

Maintenance is required monthly, conducted by a volunteer certified diver. Each month, the diver will spend roughly six hours evaluating the infrastructure of the design as well as the qualitative effectiveness. Solid plastic pollutants such as plastic bags will be removed from the structure, as well as the overall strength of the infrastructure will be noted. The limestone filter cartridges will be replaced based on the diver’s observations as well as plant trimmings or replacement. Overall cost of the labor amounts to zero as it is based on volunteer work. Each plant costs roughly fifteen dollars to replace and the limestone cartridges cost three dollars per replacement. When plants die for their natural life cycles (which should not happen frequently), they will be replaced by those divers.

Because maintenance is low, we expect the system to be able to stay and place and filter out pollutants for a rather long time, perhaps years. We will not need to replace the infrastructure or nursery components for likely decades. Over long periods of time, certain parts of other subsystems may need replacement (i.e. the fabric containing our limestone, rockwool), due to their ability to deteriorate. These are relatively easy to replace due to a modular system, however this will incur additional costs. Because of the monthly maintenance, the design should continue working smoothly barring any unforeseeable circumstances. Risks were taken into account with risk mitigation for events like fire, ice, and storms which are all low. In the event that a more beneficial material is discovered or a current material becomes obsolete, that part will require additional work to be replaced/updated, but should not require taking the system out of the water.

Great concept, and I had similar questions as above. ..
1) Wouldn’t this design be better on the muddy Diamond Creek BEFORE it enters the CO River?
2) Monthly maintenance seems high. Are the cartridges nearby (e.g., sustainable for monthly maintenance)?
3) I know you mentioned the Humpback Sucker, but can you have success criteria for fish and/or water quality?

Hi Brandon! Good concerns.
For Diamond Creek, we have previously considered placing the entire system within this branch of the river, and it does meet the ideal requirements in order to build it there. However, Diamond Creek itself is part of the Hualapai Native American Reserve, and negotiating its construction may have its own political difficulties. Therefore, we thought it to be more appropriate to place the system at the confluence between both rivers on the National Park side of the Grand Canyon, so that we can work with the Park to help filter the river.
In terms of maintenance, it is not required to replace every limestone charge and plant each month. Instead, a monthly maintenance routine is mostly the ideal time to check what needs to be replaced, and ordering the supplies to do so. We expect the limestone charges to last more than a few months, and the plants to last more than a year under standard conditions of the Colorado River. The filters will not require monthly replacements, as the lifespan of each filter cartridge depends on the acidity of the river in which the design is implemented (a more acidic river will erode the limestone at a faster rate). Each cartridge is composed of commonly found limestone CHUNKS which are available as mass retailers such as Walmart and Lowe’s, to which we expect to cost around $3 or $4 for one charge. Our previous answers may sound like a lot each month, but going in detail, it shouldn’t be.

For fish, data is taken every 1 to 10 years on varying fish populations along the Colorado River in the Grand Canyon. To see an uptick in fish population would be to see a positive benefit of this system. The main other fish present are the Flannelmouth Sucker, Bluehead Sucker, Speckled Dace and Humpback Chub, with the chub being endangered and the Speckled Dace being recently removed from this condition. The fish nursery is present in the design to encourage a safe and clean breeding ground for these fish populations to continue to rise. As for water quality, those levels (in units of NTU) are also taken every 1 to 5 years depending on the area in the Colorado River. An average NTU for a clean river is considered to be 10NTU, while the area near Diamond Creek varies extremely between 60 and 2000NTU throughout the year. To see a decrease in the NTU value would also indicate a positive effect of the design as a whole, as well as indicating the plants are removing sediment in the river.

Hi Brandon! Good concerns.
For Diamond Creek, we have previously considered placing the entire system within this branch of the river, and it does meet the ideal requirements in order to build it there. However, Diamond Creek itself is part of the Hualapai Native American Reserve, and negotiating its construction may have its own political difficulties. Therefore, we thought it to be more appropriate to place the system at the confluence between both rivers on the National Park side of the Grand Canyon, so that we can work with the Park to help filter the river.
In terms of maintenance, it is not required to replace every limestone charge and plant each month. Instead, a monthly maintenance routine is mostly the ideal time to check what needs to be replaced, and ordering the supplies to do so. We expect the limestone charges to last more than a few months, and the plants to last more than a year under standard conditions of the Colorado River. The filters will not require monthly replacements, as the lifespan of each filter cartridge depends on the acidity of the river in which the design is implemented (a more acidic river will erode the limestone at a faster rate). Each cartridge is composed of commonly found limestone CHUNKS which are available as mass retailers such as Walmart and Lowe’s, to which we expect to cost around $3 or $4 for one charge. Our previous answers may sound like a lot each month, but going in detail, it shouldn’t be.

For fish, data is taken every 1 to 10 years on varying fish populations along the Colorado River in the Grand Canyon. To see an uptick in fish population would be to see a positive benefit of this system. The main other fish present are the Flannelmouth Sucker, Bluehead Sucker, Speckled Dace and Humpback Chub, with the chub being endangered and the Speckled Dace being recently removed from this condition. The fish nursery is present in the design to encourage a safe and clean breeding ground for these fish populations to continue to rise. As for water quality, those levels (in units of NTU) are also taken every 1 to 5 years depending on the area in the Colorado River. An average NTU for a clean river is considered to be 10NTU, while the area near Diamond Creek varies extremely between 60 and 2000NTU throughout the year. To see a decrease in the NTU value would also indicate a positive effect of the design as a whole, as well as indicating the plants are removing sediment in the river.